Trends in the Change in Graphene Conductivity upon Gas Adsorption: The Relevance of Orbital Distortion

The experimental ability to alter graphene (G) conductivity by adsorption of a single gas molecule is promoting the development of ultra-high-sensitivity gas detectors and could ultimately provide a novel playground for future nanoelectronics devices. At present, the underpinning effect is broadly attributed to a variation of G carrier concentration, caused by an adsorption-induced Fermi-level shift. By means of first-principle Kubo-Greenwood calculations, here we demonstrate that adsorbate-induced orbital distortion could also lead to small but finite G conductivity changes, even in the absence of Fermi-level shifts. This mechanism enables a sound physical interpretation of the observed variable sensitivity of G devices to different chemical moieties, and it can be strongly enhanced by using a suitable Ni substrate, thereby opening new pathways for the optimal design of operational nanoscale detectors.